get rid of "No matching tables have ever been vacuumed" UNKNOWN result

[petere]

I think it's reasonable to have some kind of general check that all tables have been vacuumed or analyzed within X days. But if a database has zero tables, then the last_vacuum/last_analyze checks return UNKNOWN. This is annoying, because it breaks the ability to have this check applied uniformly without having to figure out what exactly is in the database. Having no tables in a database is not an error, and there are other checks that can be applied if one wishes to check what tables are in a database.

[maletin]

please see also: https://mail.endcrypt.com/pipermail/check_postgres/2009-April/000329.html